Workers are mourning the loss of a colleague who was killed in an industrial accident on the worksite of the new Royal Adelaide Hospital on Saturday.

The construction union said the man was crushed in an accident involving a scissor lift just after 3:00pm.

It is understood the man suffered fatal head injuries, and work on the site was halted.

The man's identity has not been released.

CFMEU SA assistant secretary Mick McDermott said the exact circumstances of the accident were not yet known but the man's colleagues were devastated.

He said too many Australians were dying on building sites.

"There's been seven or eight in Australia already this year and we're only halfway through February. It's a dangerous, dangerous game that these people work in," he said.

The death brings this year's work-related death toll in the state to five after a total of 14 fatalities were recorded in 2015.

The man's death follows that of another worker at the site in November 2014.

SafeWork SA executive director Marie Boland confirmed the state's work health and safety regulator was investigating any potential breaches of the Work Health and Safety Act.

"Every support is being offered to the family," she said.

The joint venture constructing the new hospital, Hansen Yuncken Leighton Contractors, has released a statement expressing its sympathy to the man's family and friends, and said support was being offered to workers.

"Hansen Yuncken Leighton Contractors Joint Venture (HYLC) and the entire new Royal Adelaide Hospital project team expresses its profound sympathies following a fatality involving a worker on the new Royal Adelaide Hospital construction site this afternoon," the statement read.

"Our thoughts are with family and friends of our co-worker following today's tragic events.

"HYLC is assisting Safework SA and SAPOL with their investigations. All work on the site has stopped.

"Appropriate support is being provided across the entire workforce during this very difficult time."